Added parsing ZFO and ZTG messages

[taavit]

Based on: https://gpsd.gitlab.io/gpsd/NMEA.html#_zfo_utc_time_from_origin_waypoint https://gpsd.gitlab.io/gpsd/NMEA.html#_ztg_utc_time_to_destination_waypoint

[elpiel]

Thank you for your PR! I've left some improvements notes, which should be reviewed and applied to the rest of the sentences as well.

[codecov[bot]]

Codecov Report

Patch coverage: 79.54% and project coverage change: +0.04 :tada:

Comparison is base (d8f668b) 80.22% compared to head (2fd41b3) 80.26%.

Additional details and impacted files

```diff @@ Coverage Diff @@ ## main #87 +/- ## ========================================== + Coverage 80.22% 80.26% +0.04% ========================================== Files 31 33 +2 Lines 1153 1196 +43 ========================================== + Hits 925 960 +35 - Misses 228 236 +8 ``` | [Impacted Files](https://app.codecov.io/gh/AeroRust/nmea/pull/87?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=AeroRust) | Coverage Δ | | |---|---|---| | [src/parser.rs](https://app.codecov.io/gh/AeroRust/nmea/pull/87?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=AeroRust#diff-c3JjL3BhcnNlci5ycw==) | `78.51% <0.00%> (-0.62%)` | :arrow_down: | | [src/sentences/mod.rs](https://app.codecov.io/gh/AeroRust/nmea/pull/87?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=AeroRust#diff-c3JjL3NlbnRlbmNlcy9tb2QucnM=) | `0.00% <ø> (ø)` | | | [src/sentences/zfo.rs](https://app.codecov.io/gh/AeroRust/nmea/pull/87?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=AeroRust#diff-c3JjL3NlbnRlbmNlcy96Zm8ucnM=) | `83.33% <83.33%> (ø)` | | | [src/sentences/ztg.rs](https://app.codecov.io/gh/AeroRust/nmea/pull/87?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=AeroRust#diff-c3JjL3NlbnRlbmNlcy96dGcucnM=) | `83.33% <83.33%> (ø)` | | | [src/parse.rs](https://app.codecov.io/gh/AeroRust/nmea/pull/87?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=AeroRust#diff-c3JjL3BhcnNlLnJz) | `73.86% <100.00%> (+1.24%)` | :arrow_up: | | [src/sentences/utils.rs](https://app.codecov.io/gh/AeroRust/nmea/pull/87?src=pr&el=tree&utm_medium=referral&utm_source=github&utm_content=comment&utm_campaign=pr+comments&utm_term=AeroRust#diff-c3JjL3NlbnRlbmNlcy91dGlscy5ycw==) | `100.00% <100.00%> (ø)` | |

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[elpiel]

Thank you once again for your contributions @taavit !